A naive AI for TicTacToe

package jp.co.worksap.global;

import java.util.Arrays;
import java.util.Scanner;

class Position{
int x;
int y;
public Position(int x, int y){
this.x=x;
this.y=y;
}
}
public class TicTacToe {
static final int N=3;
int grid[][]=new int

;

int curPlayer=0;
boolean isOver=false;
Scanner sc;
boolean flag;

void initialize(){
int i;
for(i=0;i<N;i++    ){
Arrays.fill(grid[i], 0);
}
sc=new Scanner(System.in);
}
boolean gameDetection(int g[][]){
int i;
for(i=0;i<N;i++){
if(g[i][0]==1&&g[i][1]==1&&g[i][2]==1) return true;
if(g[i][0]==2&&g[i][1]==2&&g[i][2]==2) return true;
if(g[0][i]==1&&g[1][i]==1&&g[2][i]==1) return true;
if(g[0][i]==2&&g[1][i]==2&&g[2][i]==2) return true;
}
if(g[0][0]==1&&g[1][1]==1&&g[2][2]==1) return true;
if(g[0][0]==2&&g[1][1]==2&&g[2][2]==2) return true;
if(g[0][2]==1&&g[1][1]==1&&g[2][0]==1) return true;
if(g[0][2]==2&&g[1][1]==2&&g[2][0]==2) return true;
return false;
}
void play(int player){
if(player==1){
Position posi=dfs_planning();
grid[posi.x][posi.y]=1;
} else if(player==2){ //human player

for(int i=0;i<N;i++){
for(int j=0;j<N;j++){
System.out.print(grid[i][j]+" ");
}
System.out.println();
}
System.out.println("Input (x,y) to play: ");
do{
int x=sc.nextInt();
int y=sc.nextInt();
if(x>=0&&x<N&&y>=0&&y<N&&grid[x][y]==0){
grid[x][y]=2;
if(gameDetection(grid)){
System.out.println("Game over. human win.");
}
break;
}
else System.out.print("Not valid position to play");
} while(true);

System.out.println("Now computer's turn.");
}
}

Position dfs_planning(){
int g2[][]=new int

;
int i,j;
for(i=0;i<N;i++){
for(j=0;j<N;j++){
g2[i][j]=grid[i][j];
}
}
for(i=0;i<N;i++){
for(j=0;j<N;j++){
if(g2[i][j]==0){
flag=false;
g2[i][j]=1;
flag=couldLose(g2, 2);
if(flag==false){
return new Position(i,j);
} else System.out.println(i+", "+j+" is not possible.");
g2[i][j]=0;
}
}
}
System.out.println("returning null");
return null;
}
boolean willLose(int g[][]){
int i;
for(i=0;i<N;i++){
if(g[i][0]+g[i][1]+g[i][2]==4 && g[i][0]*g[i][1]*g[i][2]==0) return true;
if(g[0][i]+g[1][i]+g[2][i]==4 && g[0][i]*g[1][i]*g[2][i]==0) return true;
}
if(g[0][0]+g[1][1]+g[2][2]==4 && g[0][0]*g[1][1]*g[2][2]==0) return true;
if(g[0][2]+g[1][1]+g[2][0]==4 && g[0][2]*g[1][1]*g[2][0]==0) return true;

return false;
}
boolean willWin(int g[][]){
int i;
for(i=0;i<N;i++){
if((g[i][0]==1&&g[i][1]==1&&g[i][2]==0)||(g[i][0]==1&&g[i][1]==0&&g[i][2]==1) ||(g[i][0]==0&&g[i][1]==1&&g[i][2]==1)) return true;
if((g[0][i]==1&&g[1][i]==1&&g[2][i]==0)||(g[0][i]==1&&g[1][i]==0&&g[2][i]==1) ||(g[0][i]==0&&g[1][i]==1&&g[2][i]==1)) return true;
}
if((g[0][0]==1 &&g[1][1]==1 && g[2][2]==0) || (g[0][0]==1&&g[1][1]==0&&g[2][2]==1) || (g[0][0]==0&&g[1][1]==1&&g[2][2]==1)) return true;
if((g[0][2]==1 &&g[1][1]==1 && g[2][0]==0) ||(g[0][2]==1&&g[1][1]==0&&g[2][0]==1) ||(g[0][2]==0&&g[1][1]==1&&g[2][0]==1)) return true;
return false;
}
boolean couldLose(int g2[][], int player){
int i,j,k;
k=0;
for(i=0;i<N;i++){
for(j=0;j<N;j++){
if(g2[i][j]==0) k++;
}
}
if(k==0) return false;
else {
if(player==1){
if(willWin(g2))return false;
boolean res=true;
for(i=0;i<N;i++){
for(j=0;j<N;j++){
if(g2[i][j]==0){
g2[i][j]=player;
res&=couldLose(g2, 3-player);
g2[i][j]=0;
}
}
}
return res;
} else{
if(willLose(g2)) {
return true;
}
boolean res=false;
for(i=0;i<N;i++){
for(j=0;j<N;j++){
if(g2[i][j]==0){
g2[i][j]=player;
res|=couldLose(g2, 3-player);
g2[i][j]=0;
}
}
}
return res;
}
}
}
static int fact(int n){
if(n==1) return 1;
else return n*fact(n-1);
}
public static void main(String args[]){
TicTacToe ttt=new TicTacToe();
ttt.initialize();
ttt.curPlayer=2;
while(ttt.gameDetection(ttt.grid)==false){
ttt.play(ttt.curPlayer);
ttt.curPlayer=3-ttt.curPlayer;
}

System.out.println("GAME END");
for(int i=0;i<N;i++){
for(int j=0;j<N;j++)System.out.print(ttt.grid[i][j]+" ");
System.out.println();
}
ttt.sc.close();
}
}